Quantum mechanic's impact on environment?

Factual Questions
1

I’m doing a research paper on and the interaction between economic, social, technological and environmental factors of quantum mechanics. It really is going well so far, however… I seem to be slightly at a loss when it comes to the environmental part.

How has quantum mechanics affected our environment? The only thing I have come up so far is the distant correlation from quantum mechanics => nuclear power => nuclear waste => hurting environment. No idea what else there may be… I’m trying to draw a link here and coming up with a blank.

If anyone has any suggestions at all, I would appreciate them very much. Thanks for your time everyone.
=)

2

Seeing as QM is used to descibe the behaviour of every single atom in the universe, it IS the environment.

3

Understood. But how has the discovery itself affected it? Or rather…

I see that we now understand the environment more, but how is it being affected by our understanding? I’m not entirely clear here, so bear with me folks.

4

I’d say that nuclear power is more closely tied with relativity than QM.

QM has advanced solar cell technology (small but direct effect) and anything having to do with computer chips (large number of potential secondary effects)

5

IIRC modern microcircuits involve quantum mechanical principles. This has led to landfills containing discarded electronic devices. Many (maybe all?) of these devices contain toxic materials. For example, from this article:

6

I’m not to sure on the history of nuclear physics, but I don’t believe that quantu mechanics had much impact at all on nuclear physics in it’s ealier stages as QCD was not formulated until the sixties. I’m trying to think of a technology that was based on quantum theory that has had a signifcant impact on the environment, the best i can think of are semiconductors, microprossecors, transistors, etc.

7

I’m not a biochemist, but isn’t quantum mechanics important in molecular biology, leading to advances in GM organisms, pharmaceuticals, etc? The development of genetically modified crops is pretty relevant to the environment, although I’m not sure how essential knowledge of quantum mechanics is to genetic engineering, mapping genomes, understanding the structure of proteins.

Also, if someone builds molecular-scale nanobots that destroy the planet, that would be bad for the environment.

8

Thank you all for your suggestions so far. Keep them coming!

David - I looked at that article and it looks like it might be useful. Hadn’t thought of the connection between quantum mechanics => electronical waste before. Thanks =)

9

A really tiny oil-stain in his driveway?

10

refusal: I’d have a hard time thinking of ways in which the interactions inside atoms would have a more profound effect on molecules than the interactions between atoms, which we can understand without QM.*

*We can understand it in new ways with QM, and those new ways can tie in to the interactions inside atoms, but we can make good, useful predictions about how atoms in molecules will interact without knowing about QM. Especially in the context of a biological system, where we neither have extremes of energy nor exotic particles flying around.

As for nanotechnology: It’s largely up in the air right now. Practical applications are nowhere near as exotic as creating our own lifeforms from scratch, let alone making something that could wipe out all life on Earth. There’s no good way to predict the problems we’ll have once we’ve solved the ones in front of us now, so what we prepare for will look really silly once we’ve actually reached the time we’re trying to predict.

11

A bit of a hijack, I think, but:

eh? I mean, my scientific career is devoted to understanding rigorously how atoms in molecules will interact, and I’m not aware of any theoretical tools which allow us to do that without invoking QM; the covalent bond is a QM phenomenon, surely.

[/hijack]

Along similar lines, one way in which QM might be said to influence our environment is that we can use it to help design new and interesting molecules which may have an environmental impact. As an example, other members of my research group are busily using QM to work on new rocket propellants, one of the constraints being that they have to be relatively clean. Perhaps this sort of thing would be relevant?

12

I took a course in computer-based drug design, and as refusal said Quantum Mechanics is very important. As it stands now computers are only powerful enough to computer protein/drug interactions based on the atom nucleii since it’s just 1 nucleus per atom…it’s easy to calculate that atom’s effect on nearby atoms. But we’d like to predict protein/drug interactions based on the electrons, which is where the Quantum Mechanics comes into play.

The problem is most computers today can only calculate the interactions of very small molecules since the # of calculations increases exponentially with every new atom (each electron in a molecule has some sort of effect on every single other electron). To my knowledge a quantum study of a protein would take months and years on a standard university computer.

13

What, exactly, is so important about predicting at the electron level, Bob55? Isn’t all of that complexity `hidden’ by the atom?

14

No, no, no… Everyone knows that a covalent bond is a wooden peg or a spring between a couple of painted balls ;).

But seriously, we can model molecules by non-quantum models like balls and pegs, and for the most part, those models are fairly accurate. How much difference does QM really make to that?

15

Actually, QM makes all the difference in the world; we really need the details of what electrons are doing to talk about chemistry. I’ll try to be brief, but…

It isn’t at all unreasonable to think of molecules as a bunch of atoms that interact only weakly, because this is indeed the case. And that’s the entire problem.

To elaborate a little, in my units[sup]1[/sup] the energies of quite strong chemical bonds are of order unity, while total energies of a molecule are several orders of magnitude larger.[sup]2[/sup] For instance, the total energy of the water molecule is about -76 Hartree; the total energy of all the atoms is about -75.8, and the chemical bonds therefore account for well under 0.5% of the total energy.

Clearly, the chemical bond is only a small perturbation to a molecule as a bunch of noninteracting atoms. But it’s chemical bonds that determine chemistry, of course, so we’re forced to look at the small difference of two numbers that are each several of orders of magnitude larger than the number we’re after. Clearly, no crude model can capture the small energy changes associated with chemical processes accurately enough to be useful; an error of even 1% in the total energy can mean errors of thousands of percent in energy differences. The only way I know of to treat chemical processes with any degree of predictive accuracy is to do hideously expensive QM.[sup]3[/sup]

Now, it’s relatively straightforward to calculate molecular geometry if I’m willing to pretend that molecules are a bunch of atoms connected by empirical forcefields. But if you ask for more than that, if you ask for ionization energies, or dissociation energies, vibrational frequencies, NMR coupling constants, or any of a whole host of other things an experimentalist might measure, you’re basically out of luck: you have to deal with the details of the electronic behaviour, and that means QM.

This makes a great deal of sense, because chemistry is, basically what happens when the electronic structure of a bunch of atoms changes (witness things like Lewis structures). So pretending that a molecule is a collection of atoms connected in some empirical way really means you can’t study most interesting chemical processes.
[sup]1[/sup] In quantum chemistry, we use units where the electronic charge, the electronic mass, and hbar are all equal to 1; our unit of energy (the Hartree) is thus twice the energy of the hydrogen atom. It’s a stupid system of units because everything is dimensionless, but it’s the convention.

[sup]2[/sup] To give a rough idea, the energy of an atom goes asymptotically as Z[sup]7/3[/sup], where Z is the atomic charge, if my memory isn’t failing me in my old age.

[sup]3[/sup] I’ve spent 8 hours on a Cray doing the helium atom, before, although to be fair my calculations are a lot more expensive than most, as I’m after numbers which are far more precise than we really need to worry about for most purposes.

16

Great response g8rguy, you sound like you know the professor who taught my class last year :slight_smile: He said there are only about 300 others like him in the world who actually do this sort of stuff regularly. Sometimes they all get together down and Florida at a resort and tell jokes that no one else would get. I remember a few terms like Hartree-Fock and the Fock Matrix and Z Matrix and Hessian; ahhh good times (not sure I still could pass the test and tell you what any of them mean though!).

To go a little further into Derleth’s question - yes we can predict what molecules do most of the time with current methods, but remember everything we use is just an approximation. For example, to model the bond between 2 atoms we pretend it is a spring, or to model it’s area of influence we put a sphere around it. But the problem is the spring equation, which assumes a certain curve, doesn’t take into account things like how two bonded atoms can never be super super close due to an infinite increase in energy, or after a certain distance they no longer affect one another so they separate - so we design better and better equations to approximate how atoms behave. But IIRC no matter how good the equations are, if they are based on the nuclei as a whole they are still approximations.

Quantum Mechanics doesn’t approximate (as much) - the electrons are the holy grail in predicting exactly how a molecule will behave. But of course there’s people out there who say the Quantum Mechanics we currently use is too approximative and say we need to take into account this and that, so there’s always more work to be done!

Just in case you’d like more info, here is the program we used in class, it’s called GAMESS and is completely text based (there are some GUIs out there though but are rare) and it requires very little input to solve energies - all you need are the atomic weights and every atom each atom is connected to. This website is about as boring as the program, which gives you insight into the lives of people working in Quantum Mechanics!

17

Well, I suppose I was wrong. Truly, there is more complexity in most things than I suspect.

Anyway, Bob55, GAMESS also gives us insight into what Fortran programmers are doing these days. :wink: They say it works under Linux on an Athlon, but I’m wondering if I dare subject my Compaq to the stresses that make a Cray cry uncle.

On the other hand, there’s always something to be said for stress testing…

18

Briefly, before I duck out for the weekend…

I’d love to say you could run one of these quantum chemistry codes on your PC, Derleth. You actually can, assuming you’re not going into ridiculous detail; for example, the two numbers I quoted above I generated in the course of writing the post, and not on anything like a terribly impressive computer. So don’t get the misimpression that just because we CAN make it bloody impossible to get anything done on a desktop doesn’t mean we MUST.

Bob55, I actually may know your professor, though unlikely if he’s from TN (I can’t think of anyone from there off the top of my head, but that may be because we’re not allowed to talk about TN here in Gainesville… :)). And that conference is deadly dull!